3.70:1 gears questionssssssssss

[1971ford]

is 3.70:1 gears in a 69 F100 LWB using 29.5 in. tires a bad gear ratio to allow me to have higher gas milage? meaning, are 3.70:1 gears generally bad or good on gas milage?

[ToughOldFord]

3:55's are the good ones for mileage, 4:10's for towing. 3:73 is a good compromise.

[fordman]

the smaller the numbers the better the gas mileage.

[RedneckTexan]

I've got a 3.25 in my truck and it's awesome on mileage, just can't tow anything, but, I've got a F-350 with a Dana 70 and a 4.10 gear in it for haulin/towin

[MadMaxetc]

the smaller the numbers the better the gas mileage.

For the most part yes. But don't go to low. 2.50 would lug the enine to much and actualy be worse!

3.70 to 3.50 are the best for those who want to have the best of both worlds.

I haven't heard of anyone that was happy with 3.25s. Most say the they didn't save enough on gas to justify the loss in power.

3.00s are for Autos and small tires.

[MadMaxetc]

I've got a 3.25 in my truck and it's awesome on mileage, just can't tow anything, but, I've got a F-350 with a Dana 70 and a 4.10 gear in it for haulin/towin

OK, so I guess you are the first I have heard that likes the 3.25s

[1971ford]

allright so 3.70's it is

my truck currently has a non-locking 3.25.

whats better, non locking 3.70, or locking 3.70?

[19674x4]

locking by far

[spartman]

Which style of locker then?

[SteveC]

i will say that i have 2.75 in my old ltd with a 351 ..it is good for the car...but i wouldnt want it in a truck...i kinda like my 4.11 gears in that cause i use it like a truck

[1971ford]

where can i get 3.70:1 locking gears?????

[convincor]

Here's a good calculator Ryan.
http://www.ringpinion.com/Calc_RPM.aspx

[F100builder]

It all depends on how you will use the truck. If you're running on the freeway a lot and looking for decent mileage, 3.70's aren't going to do it without an overdrive. The motor will be winding pretty high at 70mph. If you're doing a lot of towing, hauling, or stomping the gas pedal through the floor for those stoplight-to-stoplight bursts, the 3.70's or even lower are good (and fun especially with a locker! ). If you want mileage, I'd say 3.08 to 3.55 would be best. Check out Randy's Ring & Pinion at: http://www.ringpinion.com/
They have a gear ratio calculator where you plug in your engine (V6, V8, inline 6, etc.), trans (auto, 4 speed, etc.), and overall tire diameter. Then, you can play with all of the different ratios and figure your engine RPM's vs. your truck's speed. I think ideally you want a freeway RPM in the neighborhood of 1800-2100 RPM for your best mileage.
That's how I decided my gearset for the Traction-Loc 9" in my '56 with an AOD trans and a bored and stroked 396 Windsor. I went with 3.89's (tire melting with 500 ft-lbs. of torque!) but I'll have an overdrive to cruise at 70mph at 2000 RPM's. If I had gone with a non-OD trans, I would have selected a 3.55 ring & pinion.

[F100builder]

where can i get 3.70:1 locking gears?????

Gears are gears are gears. If you want a locker, you need to buy a different differential. An open diff. is a one tire spinner whereas a locker, posi, etc. will spin both rear tires. Check out Currie Enterprises, Strange, and some others I'm forgetting now . Budget wise, check your local yards for a locker.

I rebuilt my wrecking yard 9" (open diff, 2.75 gears) and saved pretty much just the case and axle housing. I bought a Trac-Loc diff. from Currie which is an original Ford diff. case with all new hardened shafts and spider gears as well as new clutches. I then bought the 3.89 gears and a Richmond master rebuild kit from Summit Racing. The rebuild kit came with all of the bearings, races, seals, crush sleeve, pinion nut, and marking compound.

[71PA_Highboy]

Ryan,

Your questions can't be answered because you haven't provided enough information.

Don't take this the wrong way, as I wish my son would ask these kinds of questions (he is 14 also), but when you ask a question like 'Which is better....?' you have to provide the context in which the answer is applicable. In the case of your question on lockers, two people could give opposite answers and BOTH be RIGHT and WRONG at the same time. They have used their personal context to answer your question, and that may not be applicable to you.

Something else to think about would be the variations of your answers... for example: types of lockers; Clutch (Trac- Lock), gear (Detroit Locker), selective (ARB or Ox) and constant (Spool). All of these have advantages and disadvantages and only YOU can determine which one is right for you as only you know what your driving style is (or will be ) and what your purpose is for building your truck.

Also, since you have 2 vehicles listed in your sig, which one should we address when you ask a question, as an F100 and F250 have some significant driveline differences (more notable when they are 4x4's)? There are some gear issues that exist with Dana axles that don't exist with the Ford 9" (Carrier/Gear compatability).

So I guess my point is that if you want a complete and useful answer tell us WHY you want the information, and what it applies to, so we can address it. (Remember the Who, what, when, where, why and how from writing class?)

Off my soap box now.

Now, I will take a stab at answering your questions.

1. are 3.70:1 gears generally bad or good on gas milage.

That would vary significantly on your engine, trans and tire size. My 4.11 and 35" tires is similar to a 3.50 and 30" tires or 3.0 and 27" tires in performance and RPM range or engine operation, so it will have NO CHANGE. If you are looking to change gears, then knowing what tires you have makes a difference. (NOTE: the tire height DOES change the aerodynamic qualities of your truck and will probably reduce MPG the taller you go)
If I were to put 35's on 'Redneck Texan's' truck, he would probably HATE it as it would be a DOG off the line or in traffic.... OK... maybe a SLUG, as a dog can actually move, and 35's with 3.25 couldn't get out of their own way.

2. my truck currently has a non-locking 3.25.

Which truck? my guess is the F100... Don't think they made a 3.25 for the D60... but I may be wrong.

3. whats better, non locking 3.70, or locking 3.70?

What are you planning to do with your truck. What are your driving conditions? I have never been to Folsom, only heard about the prison in a song once. Do you 'off-road' the truck, do you drive in a lot of 'traction compromised' situations? Is this a daily driver you just want to look cool and to race a ricer or two? For which truck?

All those matter. I wouldn't put a locker in my Highboy, but I would put an ARB in there. Also, lockers can increase tire wear and decrease mileage... do you care?

4. where can i get 3.70:1 locking gears?????

New or used, set-up or plain gears, what is your application?
I know you can get gears from Complete Offroad, but I doubt they have racing gears (they are softer steel). Do you realize what else you will need if you just get gears (or do you care as you are looking for a drop-out for a 9" not a re-gear of the D60?).

I really wanna help you, but I often don't have time to write like this, so I don't take the time to answer because I feel my answers will be out of context for your application.

Again, do not feel this is an attack directed at you, but some advice on how to get more complete, helpful and applicable answers. There are lots of people (including myself) that will shoot off a quick question without the details and then wonder why the answer they got doesn't really help.

Good luck, and feel free to ask more.

Regards,

Eric